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Ozone loss will hit health and food, says UN study

3 February 1990

By JAN SINCLAIR

THE THINNING of the ozone layer will cause problems far more serious
than rising rates of skin cancers. The first comprehensive review of research
into the effects of ozone depletion shows that food production will drop
on both land and sea, and infectious diseases will increase; further more,
the greenhouse warming is likely to be accelerated, because extra amounts
of ultraviolet radiation reaching the sea surface will diminish populations
of carbon-fixing phytoplankton.

The draft report has been compiled by the United Nations Environment
Programme’s International Committee on the Effects of Ozone Depletion. It
shows that the ozone layer is now becoming depleted. While additional research
is still needed, the report says it is clear that ozone loss poses significant
threats to human health and to the world’s ecosystems.

Phytoplankton fix more than half the carbon dioxide produced globally
each year. They are highly sensitive to increased levels of ultraviolet
radiation because they lack the protective outer layers enjoyed by higher
plant and animal species.

The report warns that the adverse effects on phytoplankton populations
will have long-term consequences for global climate and will make sea levels
rise even more than predicted.

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‘A 10 per cent decrease in carbon dioxide uptake by the oceans would
leave about the same amount of carbon dioxide in the atmosphere as is produced
by fossil fuel burning,’ the report says. The marine food web will be thrown
into disorder as plankton populations diminish and juvenile fish, crabs
and shrimp are damaged or killed by the extra ultraviolet radiation.

On land, many plant species will not grow as well as they should; germination
and flowering rates will be inhibited, and crop yields will drop.

The report also warns of possible drastic nitrogen deficiencies for
plant ecosystems like rice paddies. Organisms like the cyanobacteria which
fix nitrogen in tropical rice paddies are extremely sensitive, even to current
levels of ultraviolet radiation.

‘The annual nitrogen assimilation by this group of (prokaryotic) organisms
alone has been assumed to amount to 35 million tons, which exceeds the 30
million tons of artificial nitrogen fertiliser produced annually. The amounts
of artificial nitrogen fertiliser necessary to compensate for a substantial
loss will stress the capabilities of less developed countries.’

As far as humans are concerned, ozone depletion seems likely to increase
the number of outbreaks of infectious diseases. The report says normal immune
systems become less effective when they have been exposed to increased amounts
of ultraviolet ‘B’ radiation (UV-B). The amount of this harmful light that
reaches Earth is expected to increase as stratospheric ozone diminishes.
Outbreaks of infectious diseases like measles, herpes, tuberculosis and
leprosy can be expected to occur on a broader scale and with greater severity,
says the report.

Compounding these problems will be a reduction in the effectiveness
of vaccinations. When antigens (substances foreign to the body which stimulate
its defences) are injected through human skin that has been exposed to UV-B,
they induce tolerance to a disease, rather than immunity.

Increases in UV-B are also expected to spark a significant increase
in the development of cataracts. Unlike the skin, the eye does not develop
any tolerance to UV-B. Instead, it becomes more sensitive with repeated
exposures. For every 1 per cent depletion of ozone, an extra 100,000 people
will go blind, predicts the report.

Pollution will also become more of a problem as ozone depletion continues.
The extra ultraviolet radiation getting through to the lower layers of the
atmosphere will increase amounts of reactive radical molecules like hydroxyls
in the troposphere (the lowest layer of the atmosphere). These chemicals
could cause significant increases in levels of tropospheric ozone and other
potentially harmful pollutants like hydrogen peroxide and acids.

In addition, a range of materials will degrade faster under the increased
ultraviolet radiation. Plastics, rubber, wood, textiles and paints are all
expected to be affected. In a summary of its main concerns, the UN committee
says that additional research is needed to gain a deeper understanding of
the primary effects of ozone loss, especially in tropical and subtropical
areas where they are likely to be most marked. The summary calls for ‘global
action to prevent or mitigate the damage’.